The present invention relates generally to communications within a computer network, and more specifically, to the automatic detection of ring link provisioning errors within a communications network.
Communication in a computer network involves the exchange of data between two or more entities interconnected by communication links and subnetworks. Entities concerned primarily with the correct routing of information in the network are called routers, to distinguish them from end systems which process traffic but do not take part in routing it. There are two fundamentally different approaches to the distribution and use of routing information in a network, called Distance Vector Routing and Link State Routing. In the former, each router tells its immediate neighbors how it would reach each entity in the network, updating this as similar information is received from its neighbors. In the latter, each router arranges to send information about its own connectivity to its neighbors to all routers in the network. Each router then runs an algorithm called Shortest Path First (SPF) to find the best route from itself to each entity in the network. Early routing protocols (e.g., RIP) used the Distance Vector approach. Link State Routing protocols first appeared in the early 1980s, and became widely used in the Internet during the 1990s. OSPF (Open Shortest Path First) and Integrated IS-IS (Intermediate System—Intermediate System) are widely used examples of such protocols.
With link state routing, each router must discover its neighbors and learn their network addresses. A cost (typically related to the link bandwidth) is associated, generally by network management, with each link. One or more link state packets are then constructed containing this information, and flooded to all routers in the network. Dijkstra's Shortest Path First algorithm is then used at each router to find the shortest path to every other router. This algorithm maintains a set of nodes whose shortest path is already known and operates by adding one node to this known set with each iteration. The next step is to the next closest router along this path, always choosing the one which has the lowest cost from the local node. This process continues until all reachable nodes are in the known set with costs assigned to each.
SONET/SDH networks typically provide protection from failure by using topologies that dedicate half of the total bandwidth for protection. One type of SONET protection is bi-directional line switched ring (BLSR). The BLSR may be two-fiber or four-fiber. BLSR provides rapid restoration times with control logic. In a BLSR, traffic can be added and dropped at any node along a given ring. At the drop site, new traffic can be added to the previously used time slot and transported further around the ring. This re-use of bandwidth in a BLSR increases the capacity for the entire ring and provides many advantages over a unidirectional path switched ring (UPSR). If a fiber is cut in the BLSR, multiplexers have the speed to send the services affected via an alternate acceptable path through the ring without interruption.
When a BLSR is provisioned, each node in the BLSR has to know what other nodes are in the same ring. A user must manually check the ring provisioning to make sure the ring ID is the same from both links at a node within the ring. If there is a provisioning mismatch within the ring, the user may not know about it until route protection is utilized.
There is, therefore, a need for a method and system for automatically detecting link provisioning mismatch errors without user intervention.